In some subsea applications, production from several subsea christmas trees flows through individual flowlines from each christmas tree to a central main gathering line on the ocean floor. As new wells are drilled and completed the flowlines from these wells are also connected into the main gathering line. Making a connection between the flowlines and the main gathering line is often accomplished by using an articulated piping system having flexible ball and socket joints as shown in U.S. Pat. Nos. 3,727,954 and 3,717,920 and remote collet type connectors as shown in U.S. Pat. No. 3,096,999. In making such connections the length of the connecting pipes can be compensated to some extent by introducing swivel joints at each end of the section and in its middle as shown in the copending application Ser. No. 741,269, filed on June 5, 1985, now U.S. Pat. No. 4,696,494. Such application disclosed an improved type of swivel joint which is adapted to be used to compensate for misalignment between the subsea lines which are to be connected.
Normally telescoping joints are provided with seals to contain the fluids within the interior of the joint from leaking to the exterior and to prevent entry of surrounding fluids into the joint. In making the subsea connections mentioned above, it is desired that the length of flowline used to make such connection be adjustable so that even with multiple swivel joints there is not any stress introduced into the flowline or into the lines to which it is connected by having the connecting flowline too short, too long, or not properly aligned.
Some of the prior subsea telescopic joints have been capable of extending and shortening the flowline or spool to be used in such connections but did not have a metal-to-metal seal of the cylindrical locking surfaces of the two members of the joint. An example of this type of telescoping joint are shown in U.S. Pat. Nos. 4,138,147, 4,371,198 and 4,109,945.
Also in the past it has been suggested to use fluid pressure to bring two surfaces into frictional engagement as disclosed in U.S. Pat. No. 4,341,484. U.S. Pat. No. 4,011,918 discloses the use of hydraulic fluid injected between a drill string stabilizer and its supporting tapered pin to release frictional engagement between the stabilizer and the pin.